The Order Cyprinodontiformes is a diverse group of small to medium-sized ray-finned fishes that includes killifishes, pupfishes, livebearers (such as guppies, mollies, swordtails), and related species. They are found mainly in freshwater and brackish habitats worldwide, often thriving in warm, shallow, or even extreme environments like desert springs and hypersaline waters. Many species are known for their bright coloration and are popular in aquariums. A unique feature of this order is the presence of both egg-laying and live-bearing reproductive strategies, making them important models in studies of evolution, ecology, and genetics. Ecologically, cyprinodontiform fishes are significant as insect predators and as prey for larger animals, while some, like guppies and mosquitofish, are also used in biological control of mosquitoes.